# -*- coding: UTF-8 -*-
from typing import List
from leetcode_helper import TestcaseHelper, SolutionBase


class Solution(SolutionBase):
    # 解题的方法，命名和Leetcode的保持一致即可
    def addOperators(self, num: str, target: int) -> List[str]:
        n = len(num)
        ans = []

        def backtrack(expr: List[str], i: int, res: int, mul: int):
            if i == n:
                if res == target:
                    ans.append(''.join(expr))
                return
            signIndex = len(expr)
            if i > 0:
                expr.append('')  # 占位，下面填充符号
            val = 0
            for j in range(i, n):  # 枚举截取的数字长度（取多少位）
                if j > i and num[i] == '0':  # 数字可以是单个 0 但不能有前导零
                    break
                val = val * 10 + int(num[j])
                expr.append(num[j])
                if i == 0:  # 表达式开头不能添加符号
                    backtrack(expr, j + 1, val, val)
                else:  # 枚举符号
                    expr[signIndex] = '+';
                    backtrack(expr, j + 1, res + val, val)
                    expr[signIndex] = '-';
                    backtrack(expr, j + 1, res - val, -val)
                    expr[signIndex] = '*';
                    backtrack(expr, j + 1, res - mul + mul * val, mul * val)
            del expr[signIndex:]

        backtrack([], 0, 0, 0)
        return ans


if __name__ == '__main__':
    solution = Solution()

    # 按照leetcode的题目说明，将基本的test case填入
    # 每条case的最后一个元素是正确的结果，即期待的结果
    # 使用元组来保存输入的数据，期待的结果
    testcases = [
        ("123", 6, ["1*2*3", "1+2+3"]),
        ("232", 8, ["2*3+2", "2+3*2"]),
        ("105", 5, ["1*0+5", "10-5"]),
        ("00", 0, ["0*0", "0+0", "0-0"]),
        ("3456237490", 9191, [])
    ]

    for case_item in testcases:
        # 获取测试用的case和期待的执行结果
        input1 = case_item[0]
        input2 = case_item[1]

        expect = case_item[len(case_item) - 1]
        exec_result = solution.addOperators(input1, input2)

        # 判断执行结果，输出提示信息
        check_result = solution.check_result(expect, exec_result)
        TestcaseHelper.print_case(check_result, case_item, exec_result)
